1. Field of the Invention
The present invention relates to a speed controller, and more particularly to a speed controller of a bicycle. The speed controller has a body, a rotation element, a sleeve, a collar and a position element. The body and the rotation element are combined into one piece to eliminate the friction of the cable so as to provide a stable speed change.
2. Description of Related Art
A conventional speed controller uses a handlebar with length L to drive a cable with length I0, as shown in FIG. 6. The length of the cable is changed to I such that the length change of the cable becomes I0xe2x88x92I. With reference to FIG. 6, I0xe2x88x92I=L/cos xcex8xe2x88x92L/cos xcex80=L (1/cos xcex8xe2x88x921/cos xcex80). The purpose is to increase the rotation angle of the speed controller. However, it has its drawbacks, such as:
When the cable is driven, because the head tube is firmly fixed, a great deal of friction exists between the cable and the head tube, which causes the speed controller to be difficult to rotate.
With reference to FIG. 7, it is noted that a handlebar c extends through a conventional rotation element a and a body b. When the cable d is driven, the length change of the cable is fixed, which restricts the rotation angle of the rotation element so that it is not sufficient to efficiently accomplish the speed change. This speed controller has the following drawbacks:
1. The rotation angle of the position element e is not large enough so that friction reduces the life span of the position element.
2. To overcome the friction, the user will have to apply a large force, which makes the operation of the position element difficult.
To overcome the shortcomings of the prior art, the present invention provides an improved retaining device to mitigate or obviate the aforementioned problems.
The primary objective of the invention is to provide an improved speed controller which removes the lining of the body to reduce friction between the cable and the body.
Another objective of the invention is to provide a position element with a centrally formed protrusion to fix the relative movement between the position element and the rotation element, such that the speed change is much more accurate than with a conventional controller.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.